Polishing systems can typically include a polishing chuck which holds a work piece, and a platen upon which a polishing pad is mounted. One or more of the chuck and platen can be rotated and brought into physical contact with the other, whereby the work piece or portions thereof are abraded, ground, or otherwise polished. One problem associated with abrading, grinding or polishing work pieces in such systems, concerns uniformly removing or controlling the amount of material being removed from over the surface of a work piece.
Specifically, because of the dynamics involved in abrading work pieces, greater amounts of material can be removed over certain portions of a work piece, while lesser amounts of material are removed over other portions. Such can result in an undesirable abraded, ground, or polished profile. Yet, in other applications, it can be desirable to remove, somewhat unevenly, material from over certain portions of a work piece and not, or to a lesser degree over other portions of a work piece.
One challenge which has confronted those who process wafers is associated with retaining a wafer or work piece (which need not necessarily be a wafer), on the chuck when abrading or polishing the same. Because of the rotational velocities involved with such processing, the wafer can tend to slip off of the chuck during processing. One solution in the past has been to maintain vacuum pressure on the wafer during most or all of the processing of concern. That is, vacuum ports provided in the chuck to effect vacuum engagement of a wafer are essentially operated to maintain a vacuum relative to the wafer during abrading or polishing. However, such can cause dimpling of the wafer at these port locations which, in turn, can cause incomplete polishing of the wafer.
This invention arose out of concerns associated with providing improved uniformity in abrading, grinding, and/or polishing scenarios. In particular, this invention arose out of concerns associated with providing uniformity and flexibility in the context of semiconductor wafer processing, wherein such processing includes abrading, grinding, or otherwise polishing a semiconductor wafer or work piece.